Trajectory guide with angled or patterned guide lumens or height adjustment

ABSTRACT

This document discusses trajectory guides that include an instrument guide with at least one lumen angled with respect to an orthogonal or other through-axis. In one example, patterned lumens on the instrument guide provide a mirror image pattern of trajectory axes intersecting a target plane. In another example, height adjustment of the instrument guide extends these or other targeting techniques to a three-dimensional volume. This document also describes a method of manufacturing such an instrument guide, which is also applicable to manufacturing an instrument guide providing parallel lumens.

RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/370,090, filed Feb. 20, 2003, which application isincorporated herein by reference.

FIELD OF THE INVENTION

This document relates generally to trajectory guides, and morespecifically, but not by way of limitation, to a trajectory guide withat least one angled lumen or with patterned lumens.

BACKGROUND

Neurosurgery sometimes involves inserting an instrument through a burrhole or other entry portal into a subject's brain toward a target regionof the brain. Because of the precision needed to reach the target, whileavoiding nearby structures that are often critical to brain function,stereotactic instrument guidance is sometimes provided. In one suchtechnique, a stereotactic headframe is mounted about the patient'sskull. A trajectory guide is mounted to the headframe to provide aninstrument-guiding trajectory through the burr hole and aimed toward thetarget. In another technique (sometimes referred to as “framelessstereotaxy”), a trajectory guide is mounted directly to the skull in orabout the burr hole. The skull-mounted trajectory guide also provides aninstrument-guiding trajectory through the burr hole and aimed toward thetarget. In either technique, an image-guided workstation may be used toprovide navigational guidance to the neurosurgeon, such as by displayingpreoperative images of the subject to assist the neurosurgeon inplanning or performing the procedure.

Among other things, the present inventors have recognized that thelimited diameter of the burr hole limits the size and location of thetarget area that can be accessed via the burr hole. The presentinventors have also recognized an unmet need for reducing trauma to thebrain. For these and other reasons, which will become apparent uponreading the following detailed description and viewing the drawings thatform a part thereof, the present inventors have recognized an unmet needfor trajectory guide systems, devices, and methods that provide improvedaccess and/or reduced trauma.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsdescribe substantially similar components throughout the several views.Like numerals having different letter suffixes represent differentinstances of substantially similar components. The drawings illustrategenerally, by way of example, but not by way of limitation, variousembodiments discussed in the present document.

FIG. 1 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, a perspective view of one embodiment of aninstrument-guiding apparatus, referred to herein as a “trajectory guide”assembly.

FIG. 2 is a perspective view further illustrating, by way of example,but not by way of limitation, certain portions of an exemplarytrajectory guide assembly.

FIG. 3 is an exploded view further illustrating, by way of example, butnot by way of limitation, certain portions of an exemplary trajectoryguide assembly.

FIG. 4A is a conceptualized schematic diagram illustrating a top view ofan instrument guide having one or more parallel lumens extendingorthogonally through the instrument guide.

FIG. 4B is a conceptualized schematic diagram illustrating across-sectional side view of an instrument guide having one or moreparallel lumens extending orthogonally through the instrument guide.

FIG. 4C is a conceptualized schematic diagram illustrating across-sectional side view of an instrument guide having one or moreparallel lumens extending orthogonally through the instrument guide andhaving a limited range of motion.

FIG. 4D is a conceptualized schematic diagram illustrating a top view ofan instrument guide having at least one angled through-lumen extendingthrough the instrument guide.

FIG. 4E is a conceptualized schematic diagram illustrating across-sectional side view of an instrument guide having at least oneangled through-lumen extending through the instrument guide.

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F are cross-sectional schematic diagramsillustrating various operative embodiments of angled-lumen instrumentguides.

FIG. 6 is a conceptualized side view of an instrument guide includinglumens arranged in a predetermined pattern.

FIG. 7 is a conceptualized top view (along the cutline 7-7 of FIG. 6) ofan instrument guide including lumens arranged in a predeterminedpattern.

FIG. 8 is an example of a trajectory guide base that is custom-formedsuch that an instrument guide portion of a working platform includes anaxis extending orthogonally therethrough and directed through a burrhole or other entry portal to intersect the desired target within thesubject.

FIG. 9 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, one embodiment of a first alternativetrajectory guide base carrying an instrument guide having angledlumen(s).

FIG. 10 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of a secondalternative trajectory guide base carrying an instrument guide havingangled lumen(s).

FIG. 11 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of a thirdalternative trajectory guide base carrying an instrument guide havingangled lumen(s).

FIG. 12 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of a fourthalternative trajectory guide base carrying an instrument guide havingangled lumen(s).

FIGS. 13 and 14 are respective top and bottom perspective viewsillustrating generally, by way of example, but not by way of limitation,an alternative trajectory guide base providing, among other things, astage having an adjustable height above the entry portal.

FIG. 15 is a cross-sectional view, taken along the cutline 15-15 of FIG.14.

FIG. 16A is a cross-sectional schematic diagram illustrating generallyone example of an instrument guide having a top surface that is curved,faceted, or otherwise designed to obtain a fixed length L between a topsurface and a range plane.

FIG. 16B is a side view schematic diagram illustrating generally oneexample of an instrument having a length L and capable of being insertedthrough an instrument guide lumen.

FIG. 17 is a cross-sectional schematic drawings illustrating generallyaspects of one technique for manufacturing an instrument guide.

FIG. 18 is a cross-sectional schematic drawings illustrating generallyfurther aspects of a technique for manufacturing an instrument guide.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. Furthermore, allpublications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this documents and those documents so incorporated byreference, the usage in the incorporated reference(s) should beconsidered supplementary to that of this document; for irreconcilableinconsistencies, the usage in this document controls.

FIG. 1 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, a perspective view of one embodiment of aninstrument-guiding apparatus, referred to herein as a “trajectory guide”assembly 100. Certain portions of this example of trajectory guide 100are described in more detail in Skakoon et al. U.S. patent applicationSer. No. 09/828,451, entitled “DEEP ORGAN ACCESS DEVICE AND METHOD,”which was filed on Apr. 6, 2001, the disclosure of which is incorporatedherein by reference in its entirety, including its description of atrajectory guide that is, among other things, rotatable around an axisextending orthogonally from the skull and tiltable at an angle from saidaxis.

In FIG. 1, trajectory guide 100 includes, among other things, a base 105and an instrument guide 110. In this example, the base 105 is sized andshaped for securing in or about an entry portal 115 in a human, animal,or other subject that includes a desired target within the subjectbeyond the entry portal 115. In one example, the entry portal 115 is anapproximately circular burr hole that has been drilled or otherwiseformed in the subject's skull for accessing an underlying target regionwithin the subject's brain. In one example, the base 105 is mounted tothe skull around the burr hole entry portal 115 using bone screws. Thecircular burr hole or other entry portal 115 can be conceptualized asdefining an entry plane, e.g., tangential to the skull's outer surface,tangential to its inner surface, or tangential to a midportiontherebetween.

The instrument guide 110 can be conceptualized as including a throughaxis 120. In this particular example, axis 120 extends substantiallyorthogonally through the instrument guide 110, as illustrated in FIG. 1,such that it is directed at a center point of the entry portal 115 aboutwhich the base 105 is disposed. In this example, the instrument guide110 is coupled to the base 105 such that the instrument guide 110 iscapable of being adjustably oriented with respect to the base 105 toadjustably direct the axis 120 to extend through the entry portal 120toward the desired target. In the illustrative example of FIG. 1, aportion of the base 105 rotates concentrically about the entry portal115 and a sliding saddle 130, carrying the instrument guide 110, tiltsalong an arc portion of the base 105 to adjust the angle at which theaxis 120 intersects the tangential entry plane defined by the entryportal 115.

At least one lumen 125 extends through the instrument guide 110 forproviding an instrument-guiding trajectory path therethrough. As anillustrative example, but not by way of limitation, FIG. 1 depicts fivelumens 125A-E. The illustrative lumens 125A-E include a center lumen125A, and four offset lumens 125B-E displaced from the center lumen 125Aby at least one predetermined center-to-center distance. In theillustrative example of FIG. 1, the offset lumens 125B-E are arrangedabout the center lumen 125A (e.g., along the substantially planar orother top surface of the instrument guide 110) analogous to aNorth-South-East-West distribution pattern.

In the illustrative example of FIG. 1, the axis 120 extends coaxiallythrough the center lumen 120A, and extends substantially orthogonally ornormal to the planar or other proximal outer surface 127 of theinstrument guide 110. In this example, the instrument guide 110 includesat least one lumen (such as lumen 125E) defining a corresponding axisextending coaxially therethrough (such as a corresponding axis 135) at apredetermined angle (such as an angle 140) with the axis 120. Therefore,in this example, the nonparallel and intersecting axes 120 and 135define a plane in which the angle 140 lies. Moreover, in this example,the axes 120 and 135 intersect at a point 145 located at the entryportal, or beyond the entry portal, i.e., further within the subject.However, this is not a requirement; in an alternative example, theintersection point 145 is located above the entry portal 115, i.e.,outside of the subject. (In yet another alternative example, nonparallelaxes 120 and 135 do not intersect at all, as discussed below). In afurther example, as discussed further below, trajectory guide 100provides an adjustable height of the instrument guide 110 above theentry portal 115. By adjusting the height of the instrument guide 110above the entry portal 115, a depth (at or beneath the entry portal 115)or height (above the entry portal 115) of the intersection point 145 (ifany) can thereby be adjusted. Although the instrument guide 110 isillustrated in FIG. 1 as including five lumens 125, it is understoodthat instrument guide 110 could include a fewer or greater number oflumens 125. In addition, such lumens 125 can be configured in adifferent pattern than illustrated in FIG. 1. Moreover, in FIG. 1, oneor more of the other offset lumens 125B-E may also be configured todefine a corresponding coaxially-extending axis at a predetermined anglewith axis 120 (which angle may be the same or a different predeterminedvalue than that of the illustrated angle 140). In one example, theoffset lumens 125B-E are constructed with respective coaxially-extendingaxes at like predetermined angles with axis 120, such that these axesall intersect at a single point 145 (such as a single cortical entrypoint that is at or near the surface of the subject's brainsubstantially adjacent to the entry portal 115; this reduces corticaldamage that would otherwise result from multiple parallel tracksextending into the subject's brain). In one example, the center lumen125A is omitted, such that the axis 120 extends substantiallyorthogonally through instrument guide 110, but does not extend coaxiallythrough the center lumen 125A. In this example, the instrument guide 110includes at least one lumen defining a coaxial axis that is angled withrespect to the axis 120, as described above.

FIGS. 2 and 3 are respective perspective and exploded views furtherillustrating, by way of example, but not by way of limitation, certainportions of the exemplary trajectory guide assembly 100. In thisillustrative example, a tower-like portion of the base 105 snaps ontoand rotates upon a ring-like or other platform 300, such as by using oneor more snap-fitting side blocks 202. The side blocks 202 provide addedstability. This reduces or avoids side-to-side rocking of the tower-likeportion of the base 105 riding on a platform ring surface 302. Thecurved saddle 130 is coupled to and seated on a curved arc portion oftower-like portion of the base 105, such as by using at least onesemispheric arcuate sliding joint or the like, as illustrated. Thecurved portions of the saddle 130 and the tower-like portion of the base105 can be tilted with respect to each other to alter a trajectory angleof an instrument being introduced through the instrument guide 110. Thesaddle 130 can be secured to fix this aspect of the trajectory angle ofthe instrument into the entry plane.

In this example, an affixation mechanism, such as a thumbscrew 204,passes through an opening in the tower-like portion of the base 105 andengages a portion of the platform 300 to prevent further rotation of thetower-like portion of the base 105 with respect to the platform 300 oncea desired rotational position has been obtained. In this example, acapturing device, such as an L-shaped arm 206, retains the thumbscrew204 together with the base 105.

Another affixation mechanism, such as a thumbscrew 208A-B, passesthrough a slotted opening (tilt slot) in the saddle 130 and engages aportion of the base 105 to prevent further riding of the curved portionof the saddle 130 along the curved portion of the base 105 once adesired trajectory angle has been obtained. This example also includesattachment fasteners 210A-B passing through corresponding slots in thesaddle 130 for additionally securing the saddle 130 to the base 105. Inthis illustrative example, the attachment fasteners 210A-B includescrews passing through respective retainer brackets, each of whichincludes a curved surface conforming to a curved surface of the saddle130.

Also in this example, an interior portion of a socket or otherreceptacle 212 on the saddle 130 provides a socket portion of aball-and-socket joint. An affixation mechanism, such as a thumbscrew214, passes through a threaded opening in the socket 212 to secure theposition of a ball 304 housed therein. The socket 212 also includesfine-tuning thumbscrews 216A-C, which pass through threaded openings inthe socket 212 for further adjusting the exact position of the ball 304within the socket 212. The socket 212 further carries the instrumentguide 110. In this example, the instrument guide 110 includes a taperedbarrel sleeve 306 that is releasably coupled, such as by release tab 218and associated structure(s), within a cylindrical opening 310 throughthe ball 304.

However, in an alternative example, the ball 304 is omitted, and thebarrel sleeve 306 is sized and shaped to be received directly within thecollar of the receptacle 212. In one such example, the fine-tuningthumbscrews 216A-C are also omitted. In another such example, thefine-tuning thumbscrews 216A-C are replaced by a single thumbscrew,e.g., the thumbscrew 216A. In a further example, the barrel sleeve 306includes threads mating to threads on an interior portion of thereceptacle 212. This implements an adjustable coupling device thatadjustably couples the instrument guide 110 to the base 105. Forexample, this allows adjustment of the height of the instrument guide110 above the entry portal 115 by screwing the barrel sleeve 306 intothe threaded receptacle 212 by an appropriate amount. In anotherexample, the height is adjusted by inserting a non-threaded barrelsleeve 306 into a non-threaded receptacle 212 by the desired amount.Then, barrel sleeve 306 is locked down, such as by tightening thethumbscrew 216A, or by using any other suitable fixation technique.

In the example of FIG. 3, to release the instrument guide 110 from theball 304, the tab 218 is pressed inward toward the sleeve 306. Thisforces or wedges a portion of the release tab 218 against a top portionof the ball 304 and aids in releasing the instrument guide 110 from theball 304. The top portion of the instrument guide 110 provides at leastone instrument-guiding lumen 125, such as discussed above with respectto FIG. 1. In this example, the instrument guide 110 also includesT-shaped receptacles or recesses 220A-D for receiving further attachableequipment. In one embodiment, the instrument guide 110 (or an apparatuscoupled thereto) includes one or more fiducial markers (e.g., LEDs,reflectors, microcoils, MR-visible components, or other locators), suchas for assisting the user in obtaining the desired trajectory alignmentin a frameless surgical navigation system and/or in an MRI environment.

In the examples of FIGS. 1-3, a portion 150 of the tower-like base 105is left open, allowing viewing of the entry portal 115. Moreover, thisadvantageously permits viewing and/or access of any instruments beinginserted through the entry portal 115. In one example, as illustrated inFIGS. 1-3, the open portion 150 is facilitated by restricting the saddlemovement of saddle 130 such that, when the base 105 is fixed withrespect to the platform ring 302, the saddle movement adjusts the anglebetween axis 120 and an axis normal to the entry portal 115 in a singledirection from the axis normal to the entry portal 115, rather than intwo directions with respect thereto. However, this represents merely onetechnique of leaving the entry portal 115 viewable and/or accessible; acutout portion of the instrument guide 110, or any other viewing and/oraccess technique may alternatively be used.

FIGS. 4A, 4B, 4C, 4D, and 4E are conceptualized schematic diagramsillustrating a top view 400 (FIG. 4D) and side view 405 (FIG. 4E) of aninstrument guide 410 having at least one angled through-lumen, incomparison to a top view 420 (FIG. 4A) and side view 425 (FIG. 4B) of aninstrument guide 430 having one or more parallel lumens extendingorthogonally through the instrument guide 430. In this conceptualizedschematic diagram, the instrument guides 410 and 430 are illustrated,for conceptual clarity, without being coupled to a respective base thatis attached to the subject. However, it is understood that, inoperation, the instrument guides 410 and 430 may be coupled to atower-like base 105 or any other skull-mounted or frame-mounted basediscussed in this document or known in the art. FIGS. 4B, 4C, and 4Eillustrate respective burr hole entry portals 435A-B, in a subject'sskull 440A-B, above which instrument guides 410 and 430 are respectivelymounted.

In one example, such as discussed above with respect to FIG. 1,instrument guides 410 and 430 are coupled to the base 105 having arotational joint (such as provided by the platform ring surface 302) andan arcuate sliding joint (such as provided by the saddle 130). In thismanner, respective bottom surfaces 445A-B of the instrument guides 410and 430 define respective planes tangential to semispheres 450A-B sweptby adjusting the rotational and arcuate orientations provided by thebase 105. In this example, the instrument guides 410 and 430 includerespective top surfaces 455A-B defining respective planes that aresubstantially parallel to those defined by respective bottom surfaces445A-B, however, the invention is not so limited, as discussed below.

In this example, the instrument guide 410 includes at least oneinstrument-guiding lumen 460A-E extending through the instrument guide410 at an angle with respect to an axis 465A that extends through theinstrument guide 410 aimed at the center of the entry portal 435A. (Inone example, axis 465A is also orthogonal to one or both of the planesdefined by the top surface 455A and the bottom surface 445A of theinstrument guide 410). By contrast, the instrument guide 430 includesinstrument-guiding lumens 470A-E extending through instrument guide 430parallel to an axis 475A that extends through instrument guide 430 aimedat the center of the entry portal 435B. (In one example, axis 475A isalso orthogonal to one or both of the planes defined by the top surface455B and the bottom surface 445B. orthogonal to the planes defined byits top surface 455B and its bottom surface 445B of the instrument guide430.) In the example illustrated in FIGS. 4A-4E, lumens 460A-E definecorresponding coaxial trajectory axes 465A-E, and lumens 470A-E definecorresponding coaxial trajectory axes 475A-E. These axes are illustratedas extending through respective entry portals 435A-B and intersectingrespective target range planes 480A-B that are located within thesubject at a distance Z from the respective bottom surfaces 445A-B.

The instrument guide 430 includes the offset lumen 470D, which isseparated from the center lumen 470A by a distance d along the topsurface 455B. Because these lumens define parallel axes 475A and 470D,such axes intersect target plane 480B with the same radial separation d,as illustrated in FIG. 4B. Moreover, because the instrument guide 430 ispositioned at a distance above a burr hole entry portal 435B of alimited diameter, the adjustable orientation of the instrument guide 430using the arcuate tilting of the saddle 130 will only be able to reach arelatively limited range of points on the target plane 480B, as depictedin FIGS. 4B and 4C.

The instrument guide 410 includes the offset lumen 460D, which isseparated from the center lumen 460A by a like distance d along the topsurface 455A. However, the coaxial axes 465D and 465A defined by therespective lumens 460D and 460A are configured to intersect at a commonfocus point 485, which is typically located at or beyond entry portal435A (e.g., within the subject), but which can alternatively be locatedoutside the subject above the entry portal 435A. This results in theaxes 465D and 465A intersecting target plane 480A at points separated bya distance D. The angle between the axes 465D and 465A can be selectedsuch that (for a given distance Z between the bottom surface 445A of theinstrument guide 410) the axes 465D and 465A intersect the target plane480A at the separation distance D, where the separation distance D atthe target plane 480A is capable of exceeding the separation distance dat top surface 445A of the instrument guide 410. Moreover, the distanceD is not limited to the radius of the burr hole entry portal 435A, butmay instead exceed the radius of the burr hole entry portal 435A.Furthermore, using the arcuate tilting of the saddle 130, an evengreater range of points on the target range plane 480A will beaccessible by using the instrument guide 410. In addition, theinstrument guide 410 will be able to accommodate more arcuate tiltingthan the instrument guide 430 because the angled trajectory axes aremore focused within the entry portal 435A than the parallel trajectoryaxes are within the similarly-sized entry portal 435B. This will furtherextend the accessible area on target plane 480A beyond that accessibleon target plane 480B. Additionally or alternatively, the focusedtrajectory axes allow use of a smaller burr hole 435A, as illustrated inFIG. 4E.

In the illustrative example of FIG. 4D, the instrument guide 410includes a center lumen 460A (labeled “C” in FIG. 4D), defining acorresponding coaxial trajectory axis 465A aimed at the center of entryportal 435A. In this example, a “right” offset lumen 460D (labeled “R”in FIG. 4D), defining a corresponding coaxial trajectory axis 465D, isseparated from the center lumen 460A at the top surface 455A by acenter-to-center distance d. In this example, a “left” offset lumen 460B(labeled “L” in FIG. 4D), defining a corresponding coaxial trajectoryaxis 465B, is separated from the center lumen 460A at the top surface455A by a like center-to-center distance d. In this example, a“posterior” offset lumen 460E (labeled “P” in FIG. 4D), defining acorresponding coaxial trajectory axis 465E (not shown), is separatedfrom the center lumen 460A at the top surface 455A by a likecenter-to-center distance d. In this example, an “anterior” offset lumen460C (labeled “A” in FIG. 4D), defining a corresponding coaxialtrajectory axis 465C (not shown), is separated from the center lumen460A at the top surface 455A by a like center-to-center distance d. Axes465A-E intersect at a focus point 485. In the illustrative example ofFIG. 4E, the focus point 485 is located at the entry portal 435A.However, the focus point 485 can alternatively be located at or beyondentry portal 435A (i.e., within the subject), or even located outsidethe subject above the entry portal 435A. For example, the focus point485 may be located beyond the entry portal 435A, i.e., deeper within thesubject, either by: (1) altering the angle between the offset lumens460B-E and the orthogonal center axis 460A; or (2) altering the heightof the instrument guide 410 above the entry portal 435, or both (1) and(2).

In one example, trajectory guide assembly 100 is prepared as a kitproviding multiple different instrument guides 110. Each instrumentguide 110 in the kit provides a predetermined distance d and apredetermined offset lumen angle 140 that obtains a different resultingpredetermined distance D at a given height of the instrument guide 110above the entry portal 115. In a further example, the height of theinstrument guide 110 above the entry portal 115 is also adjustable.This, in turn, adjusts the depth of the focus point 485. For example, inoperation in a brain surgery application, positioning the focus point485 at a single cortical entry point just beneath the entry portal 435Areduces trauma to the subject's brain.

In one example, the height of the instrument guide 110 above the entryportal 115 is adjusted by inserting a washer-like spacer (having apredetermined thickness) over the barrel sleeve 306 of the instrumentguide 110 before the barrel sleeve 306 is inserted into the opening 310in the ball 304. In this example, the trajectory guide assembly 100 isprepared as a kit with multiple spacers of different predeterminedthicknesses to adjust the height of the instrument guide 110 above theentry portal 115. The user can select the appropriate spacer thatadjusts the height of the instrument guide 110 above the entry portal115 to obtain, for example: the desired depth of focus point 485; thedesired depth of the target plane 480A corresponding to thepredetermined distance D; or, to adjust the value of D for a targetplane 480A at a given depth beneath the entry portal 435A. In oneexample, the trajectory guide kit includes printed instructions or acomputer program providing the necessary computations to assist the userin selecting the appropriate height of the instrument guide 110 forobtaining the desired access to accomplish one or more of these variousobjectives. In a further example, at least some of such information isprinted on the spacers.

FIGS. 5A-5F are cross-sectional schematic diagrams illustratingconceptually various operative embodiments of an instrument guide havingat least one angled through-lumen. In FIG. 5A, the instrument guide 410Ais positioned such that its top surface is at a height H1 above theentry portal 435A in the skull 440A. The target plane 480A is located ata distance Z1 below the bottom surface of the instrument guide 410. Inthis example, the lumens 460 are configured to intersect at a singlecortical entry point 485 at the surface of the subject's brain justbeneath the entry portal 434A. Using this single cortical entry point485 reduces trauma to the subject's brain. The axes 465A and 465D areseparated by a distance d at the top surface of the instrument guide410, as are the axes 460A and 460B. The axes 465A and 465D intersect thetarget plane 480A at points that are separated by a distance D1, as dothe axes 460A and 460B.

In FIG. 5B, the instrument guide 410A is positioned closer to the entryportal 435A (i.e., H2<H1) and/or the angles between the axes 465A and465D and between the axes 465A and 465B are decreased (as compared toFIG. 5A). Consequently, the axes 465A, 465B, and 465D intersect at asingle focus point 485 located beyond entry portal 435A within thesubject. This deeper focus point 485 may be useful, for example, toavoid a nearby critical area 500 that may be located at least partiallybeneath the entry portal 435A.

In FIG. 5C, the instrument guide 410A is positioned farther from theentry portal 435A (i.e., H3>H1) and/or the angles between the axes 465Aand 465B are increased (as compared to FIG. 5A). Consequently, the axes465A, 465B, and 465D intersect at a single focus point 485 located abovethe entry portal 435A and outside the subject. In this example, becausethe axes are still more focused within the entry portal 435A than theparallel axes of the instrument guide 430 of FIG. 4B, the embodiment ofFIG. 5C still obtains wider accessibility of points on the target plane480A than would the parallel axes of the instrument guide 430 of FIG.4B.

FIG. 5D illustrates an example in which lumens 461A, 461B, and 461Dthrough instrument guide 410B define corresponding coaxial axes 465A,465B, and 465D need not, and do not, intersect at a single focus point.Instead, the axes 465A and 465B intersect at a point 485B, and the axes465A and 465D intersect at a different point 485A, and the axes 465B and465D intersect at yet another point 485C.

FIG. 5E illustrates an example in which the center lumen 460A is omittedfrom instrument guide 410C. In this example, the instrument guide 410Cincludes at least one lumen, such as the lumen 462D defining a coaxialaxis 465D that intersects, at a focus point 485, an orthogonal axis 465Athrough top and bottom surfaces of the instrument guide 410C. Thisexample may be useful, for example, in obtaining access to points beyondthe radius of the burr hole entry portal 435A.

FIG. 5F illustrates an example in which none the axes 465A, 465B, and465D through instrument guide 410D intersects another one of the axes465A, 465B, and 465D. This example may be useful, for example, ininserting needles or other instruments concurrently into each of thelumens 463A, 463B, and 463D respectively corresponding to the axes 465A,465B, and 465D. Alternatively, at least one of the axes 465A, 465B, and465D does not intersect another one of the axes 465A, 465B, and 465D.FIGS. 5A-5F are merely illustrative examples; other variations are alsopossible.

FIGS. 6 and 7 are a conceptualized side view (FIG. 6) and a top view(FIG. 7), respectively, of an instrument guide 600 including lumens605A-G arranged in a predetermined pattern 615 that is a mirror image ofa desired pattern 620 in a target range plane 630, which is parallel toan entry plane 635 defined by the entry portal 435A. Lumens 605A-Gdefine respective coaxial axes that converge upon and intersect at focuspoint 485, which, in this example, is located on the surface of thesubject's cortex 625 adjacent to and just beyond the entry portal 435A.The coaxial axes defined by the lumens 605A-G intersect the target plane630 in the desired pattern 620 for which the mirror image pattern 615was designed to obtain.

In one example, the desired pattern 620 represents an anatomical,pathological, or other clinically relevant feature within the brain. Inone illustrative example, the desired pattern 620 may be shapedsimilarly to a tumor or lesion, having a particular shape, for whichtreatment by a primary instrument (guided by instrument guide 600) isdesired. In another illustrative example, the desired pattern 620 isshaped like the subject's putamen and/or caudate nucleus—anatomicalregions of the subject's brain that may benefit from, among otherthings, transplanted fetal nigral cells for treating Parkinson'sdisease. Similarly, mirror image guide lumen pattern 615 may beconfigured to obtain any other desired pattern shape 620 and/or targetdistribution at a particular depth, whether to match an anatomical orpathological feature or to obtain any other clinically desirableinstrument access. Moreover, by adjusting a height of instrument guide600 above entry portal 435A, the same pattern shape 620 can be obtainedin three dimensions for various target range planes 630 located atdifferent depths beneath entry portal 435A. Alternatively oradditionally, trajectory guide assembly 100 is configured as a kit withmultiple instrument guides 600 for obtaining the same or differentpatterns 620 at the same or different depths beneath entry portal 435A.

Although FIGS. 6 and 7 were discussed above with respect to aninstrument guide 600 having a predefined pattern of holes thatcollectively obtain a desired pattern on a target range plane 630, in analternate example, a “multipurpose” or “universal” instrument guide 600is used. Such a multipurpose instrument guide 600 select between morethan one target pattern on the target range plane 630. In one example,the particular resulting target pattern results from which particularones of lumens 605 are selected for inserting an instrumenttherethrough. In one such example, a printed user manual (or computersoftware) is used to instruct the user which particular lumens to selectand utilize for inserting the instrument (and/or which particular lumensto avoid using) thereby obtaining the desired pattern. In one example,the user marks those lumens through which the instrument will beinserted by pressing a colored (or otherwise identifiable) guide bushinginto such selected lumens (or alternatively, by inserting a plug intothose lumens that are to be avoided for obtaining the desired pattern).In one example, the tops of such lumens are countersunk to receive suchguide bushings.

Other Exemplary Bases

FIGS. 1-3 illustrate an example of the instrument guide 110 used inconjunction with one example of the base 105, however, the instrumentguide 110 may be used with a wide variety of skull-mounted orframe-mounted bases. FIGS. 4-7 illustrate operative examples ofinstrument guides 410 and 600 that are independent of the particularbase used for the instrument guide.

FIG. 8 is an example of a trajectory guide base 800 that iscustom-formed (e.g., using known rapid prototyping and toolingtechniques and preoperative images of a desired target in a subject)such that an instrument guide 805 portion of a working platform 810includes a center axis 815 (e.g., extending orthogonally therethrough)wherein center axis 815 is directed through the center of a burr hole orother entry portal such that center axis 815 intersects a portion of thedesired target within the subject. In one example, platform 810 isoriented as desired by customizing the size or shape of legs 820, whichare mounted to the subject's skull, such as by using bone screwsextending through holes 825 through respective feet 825 extendingoutwardly from respective legs 820. In this example, instrument guide805 includes at least one instrument-guiding lumen 835, which defines acoaxial axis therethrough that is angled with respect to center axis 815(e.g., as discussed above). In one example, multiple differentinstrument guides 805 are capable of being snap-fitted or otherwiseinserted into platform 810, providing lumens defining different coaxialpatterns and/or providing various heights of the top surface of theinstrument guides 805 above the entry portal. In a further example, suchinsertion of one or more instrument guides 805 into platform 810 usesone or more spacers, an adjustable coupling, or any other heightadjustment device. Base 800, or any of the other bases discussed in thisdocument, may be mounted to skull-mounted fixtures for carrying fiducialmarkers recognizable on an imaging system, such as a frameless surgicalnavigation system, a magnetic resonance imaging system, etc.

FIG. 9 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, one embodiment of an alternativetrajectory guide base 900 carrying an instrument guide 905 having atleast one lumen that is angled with respect to a center axis aimed atthe center of the underlying entry portal. In one example, instrumentguide 905 configured substantially as described above with respect toinstrument guide 410, and having a barrel sleeve portion 910 such asdescribed above with respect to instrument guide 110. Certain portionsof trajectory guide base 900 are described in Matthew Solar's U.S.patent application Ser. No. 10/325,615, entitled ORGAN ACCESS DEVICE ANDMETHOD, filed on Dec. 20, 2002, assigned to Image-Guided Neurologics,Inc., which is incorporated herein by reference in its entirety,including its description of a trajectory guide base as illustrated inFIG. 9 of the present document.

FIG. 10 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of analternative trajectory guide base 1000 carrying an instrument guide 1005having at least one lumen that is angled with respect to a center axisaimed at the center of the underlying entry portal, e.g., such asdescribed above with respect to instrument guide 410. Certain portionsof trajectory guide base 1000 are described in Matthew Solar's U.S.patent application Ser. No. 10/325,615, entitled ORGAN ACCESS DEVICE ANDMETHOD, filed on Dec. 20, 2002, assigned to Image-Guided Neurologics,Inc., which is incorporated herein by reference in its entirety,including its description relevant to a trajectory guide base asillustrated in FIG. 10 of the present document.

FIG. 11 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of analternative trajectory guide base 1100 carrying an instrument guide 1105having at least one lumen that is angled with respect to a center axisaimed at the center of the underlying entry portal, e.g., as describedabove with respect to instrument guide 410, and having a barrel sleeveportion 1110 such as described above with respect to instrument guide110. In this example, barrel sleeve 1110 extends into a ball 1115 thatis received within a socket 1120 portion of base 1100. In this example,ball 1115 is positioned just above a burr hole entry portal. Certainportions of trajectory guide base 1100 are described Truwit U.S. Pat.No. 6,267,769, which is incorporated herein by reference in itsentirety, including its description relevant to a trajectory guide baseas illustrated in FIG. 11 of the present document.

FIG. 12 is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, another embodiment of analternative trajectory guide base 1200 carrying an instrument guide 1205having at least one lumen that is angled with respect to a center axisaimed at the center of the underlying entry portal, e.g., as describedabove with respect to instrument guide 410, and having a barrel sleeveportion 1210 such as described above with respect to instrument guide110. In this example, barrel sleeve 1210 extends into a ball 1215 thatis received within a socket 1220 portion of base 1200. In this example,ball 1215 is positioned at least partially within a burr hole entryportal. Certain portions of trajectory guide base 1200 are describedTruwit U.S. Pat. No. 5,993,463, which is incorporated herein byreference in its entirety, including its description relevant to atrajectory guide base as illustrated in FIG. 12 of the present document.

FIGS. 13 and 14 are respective top and bottom perspective viewsillustrating generally, by way of example, but not by way of limitation,an alternative trajectory guide base 1300, similar in certain respectsto the base 105 of FIG. 1 (e.g., capable of rotatably riding on aplatform ring and including an arcuate saddle movement for tilting atrajectory angle with respect to a normal axis from center of the entryportal). In the examples of FIGS. 13 and 14, the base 1300 includes arotatable cylinder 1301 having an arced upper end upon which a tiltingsaddle 1340 rides. The saddle 1340 includes an upwardly extendingcylinder 1302. A rotatable dial 1325 rests upon a top end of thecylinder 1302. The dial 1325 is captured against the top end of thecylinder 1302 by an overlying plate-like retainer collar 1303. Thecollar 1303 is secured to the saddle 1340 by screws 1304A-D, which arereceived into corresponding screw mounts 1306A-D, which rise upward fromthe saddle 1340.

In this example, the trajectory guide base 1300 includes a receptacle1305 that is sized and shaped to receive a barrel sleeve (or otherportion) of an instrument guide. In one example, the received instrumentguide includes at least one lumen that is angled with respect to acenter axis aimed at the center of the underlying entry portal, e.g., asdescribed above with respect to the instrument guide 410. In the exampleillustrated in FIGS. 13 and 14, the base 1300 includes a stage 1310. Thestage 1310 includes an outwardly protruding sleeve 1315 through whichthe receptacle 1305 extends. In this example, the sleeve 1315 includesexternal threads 1320 that engage corresponding internal threads on acaptured rotatable receiving collar dial 1325. In this example, the dial1325 includes ridges, texture, or other features that make it easier togrip and rotate the dial 1325. By rotating the dial 1325, the stage 1310rides up or down on the internal threads of the dial 1325. In thismanner, the dial 1325 and the threads 1320 of the sleeve 1315 provide anadjustable coupling device for adjusting a height of the stage 1310above the entry portal. This, in turn, adjusts the height of the topsurface of any instrument guide that is inserted into the stage 1310.When the desired height is obtained, that height is secured by turning anut 1326, which, in turn, wedges an underlying bushing against sleeve1315.

In one example, an interior portion of the receptacle 1305 includescircumferential gear teeth 1330 that mate with and engage correspondingcircumferential gear teeth on a cylindrical outer portion of theinstrument guide inserted therein. This prevents the instrument guidefrom rotatably slipping within the receptacle 1305 unless the instrumentguide is intentionally lifted out, rotated, and re-inserted into thereceptacle 1305. This example also includes a cutout portion of thesaddle 1340 riding on an arcuate joint of base 1300. This allows viewingand access of the instrument being inserted through the instrument guidereceived in receptacle 1305, as discussed above. Such viewing and accessenhances both safety and usability of any surgical or other proceduresbeing performed using the instrument.

FIG. 15 is a cross-sectional view, taken along the cutline 15-15 of FIG.14. Among other things, FIG. 15 illustrates further details relevant tothe adjustable height coupling for varying the height of the stage 1310above the entry portal. FIG. 15 further illustrates one example of howthe dial 1325 is captured between the underlying cylinder 1302 and theoverlying collar 1303. In this example, the collar 1303 is secured tothe saddle 1340 via screws 1304A-D that are inserted into correspondingscrew mounts 1306A-D. The internal cylindrical circumference of the dial1325 includes one or more threads 1500 that engages one or more of thethreads 1320 on the external cylindrical circumference of the sleeve1315 upon which the stage 1310 rests. Using such a threaded adjustableheight coupling, the sleeve 1315 (and the attached stage 1310) is movedup and down by rotating the dial 1325.

In the example of FIG. 15, the collar 1303 includes an upwardly risingcylinder 1505. An external circumference of the cylinder 1505 includesone or more threads 1510. An internal circumference of the cylinder 1505is tapered, such as to receive an approximately circular or cylindricalwedge bushing 1515 therein. The nut 1326 includes internalcircumferential threads 1520 that engage the external circumferentialthreads 1510 of the cylinder 1505. After the height of the stage 1310 isthreadably adjusted, such as discussed above, the resulting height issecured by rotating the nut 1325, which forces the wedge bushing 1515downward and inward against the sleeve 1315.

The example of FIG. 15 also illustrates an instrument guide 1525inserted within the sleeve 1315. In one example, instrument guide 1525includes at least one instrument-guiding through lumen that is angledwith respect to an axis aimed at the center of the underlying burr holeentry portal. However, it should be understood that the heightadjustment mechanism illustrated in FIG. 15 can also be used with aninstrument guide 1525 having lumens 1530A-C that are at or parallel toan axis aimed at the center of the underlying burr hole entry portal,such as illustrated in FIG. 15.

Range-Compensated Instrument Guide Example

FIG. 16A is a cross-sectional schematic diagram, similar in certainrespects to that of FIG. 5A, but illustrating generally one example ofan instrument guide 1600 having a top surface 1605 that is curved,faceted, or otherwise designed to obtain, for each axis 465A-D extendingcoaxially through a corresponding trajectory guide lumen 460A-D, a fixedlength L between the top surface 1605 and a range plane 480A that isparallel to the entry plane that is tangential to the burr hole or otherentry portal 435A. This allows a biopsy needle 1610 (or otherinstrument) having a length L (for example, fixed by setting a depthstop 1615), as illustrated in FIG. 16B, to be inserted through any ofthe lumens 460A-D (e.g., using a handle 1617). The distal tip 1620 willreach the target plane 480A-regardless of the particular lumen 460A-Dthrough which the needle 1610 is inserted), despite the fact that someof these axes 465B-D are angled with respect to an axis 465A that isaimed at the center of the entry portal 435A.

Example of Manufacturing Instrument Guide

FIGS. 17 and 18 are cross-sectional schematic drawings illustratinggenerally, by way of example, but not by way of limitation, onetechnique for manufacturing an instrument guide having at least oneangled lumen (such as the instrument guide 410, for example). However,the devices and techniques illustrated in FIGS. 17 and 18 are alsouseful for manufacturing an instrument guide having parallel lumens(such as the instrument guide 420, for example).

In the example illustrated in FIG. 17, a molding plug/bushing 1700 isfirst inserted into a fixture 1702. In this example, the bushing 1700 isa plastic or other hollow cylinder including a lumen 1704 and aring-like circumferential lip 1706. In this example, the bushing 1700defines the outer circumferential shape of the completed instrumentguide 410. The fixture 1702 includes a circular base 1708 and acircumferential seating ring 1710 rising orthogonally outward therefrom.The ring 1710 is sized and shaped to snugly receive the bushing 1700therewithin. The fixture 1702 includes insertable and removable rods orpins 1712A-E. Such pins 1712A-E will define the corresponding lumens460A-E of the completed instrument guide 410, as discussed below. In theillustrated example, the removable pins 1712A-E are inserted snuglywithin respective appropriately oriented receptacles 1714A-E in thecircular base 1708, with such insertion occurring either before or afterthe bushing 1700 is seated within the ring 1710 of the fixture 1702.

In FIG. 18, tubes 1800A-E are then slipped over the respective pins1712A-E. The lumens of these tubes 1800A-E will provide thecorresponding lumens 460A-E of the completed instrument guide 410. Inone example, the tubes 1800 are thin metal tubes having a wall thicknessof about 0.003 inches.

After the hollow tubes 1800A-E have been slipped over the respectivepins 1712A-E, the interstices between the tubes 1800A-E, e.g., withinthe lumen 1704 of the bushing 1700, are filled with liquid epoxy (or anyother flowable hardening agent). This epoxy solidifies to form a solidplug 1802. The solid plug 1802 holds and carries the tubes 1800A-E inthe orientation defined by their respective pins 1712A-E. The pins1712A-E are then removed from the base 1708 of the fixture 1702. Thelumens of the tubes 1800A-F then provide the respective lumens 460A-E ofthe completed instrument guide 410. The completed instrument guide 410(which includes the bushing 1700, the tubes 1800A-E, and the solid plug)is then removed from the fixture 1702.

The above described method of manufacture is well-suited formanufacturing an instrument guide 410 having one or more angled lumens,which would generally be incompatible with a plastic molding process.Moreover, drilling such lumens is limited by the accuracy of drilling,which may be subject to wander of the drill bit. The above describedmethod of manufacture is also well-suited for manufacturing aninstrument guide 420 having parallel lumens. Although parallel lumensare not wholly incompatible with a plastic molding process, such aplastic molding process would likely result in tapered lumens. Bycontrast, the tubes 1800A-E are capable of providing lumens of uniformcircumference. Moreover, the above described method is applicable tomanufacturing an instrument guide having any number of one or morelumens used for providing trajectory guidance or for any other purpose.

CONCLUSION

The various bases discussed in this document are presented asillustrative examples, and are not intended to be limiting. Theinstrument guides discussed in this document that have at least onelumen angled with respect to a center axis aimed at the center of theunderlying entry portal will be capable of use with other skull-mountedor frame-mounted bases. Moreover, the techniques discussed herein arenot limited to targeting locations within a subject's brain, but arealso applicable to targeting other locations within a subject.Furthermore, the techniques discussed herein may also be useful foraccessing locations within any material, particularly where access tothe material is limited by a finite-sized entry portal.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments may be used in combination with each other. Many otherembodiments will be apparent to those of skill in the art upon reviewingthe above description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. In the appendedclaims, the terms “including” and “in which” are used as theplain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

1. A method comprising: securing an apparatus having a base and aninstrument guide relative to an entry portal of a subject, theinstrument guide defining a first lumen having a first axis and a secondlumen having a second axis, the first and second axes being fixedrelative to each other at a nonzero first angle; moving a position ofthe instrument guide with respect to the base and the entry portal suchthat the first axis passes substantially through a center of the entryportal toward a target in the subject and such that a second trajectorythrough the instrument guide along the second axis is directed throughthe entry portal, wherein the moving the position of the instrumentguide includes selecting the first angle to provide a predeterminedoffset distance between intersection points of the first and second axeswith a range plane, beyond the entry portal, that is substantiallyorthogonal to the first axis; and adjusting a height between theinstrument guide and the entry portal to adjust a distance between theentry portal and the range plane corresponding to the predeterminedoffset distance.
 2. The method of claim 1, further comprising providinga first trajectory through the instrument guide along the first axis. 3.The method of claim 1, wherein the moving the position of the instrumentguide includes locating the second axis such that the first and secondaxes intersect at a point, within the subject, that is located at orbeyond the entry portal.
 4. The method of claim 1, which thepredetermined offset distance exceeds a radius of the entry portal. 5.The method of claim 1, further comprising providing a plurality ofdifferent trajectories through the instrument guide along correspondingaxes intersecting a range plane beyond the entry portal, the range planebeing substantially orthogonal to the first axis, the intersectionpoints with the range plane of the axes of the trajectories forming ascaled mirror image of intersection points between the axes of thetrajectories and a plane through the instrument guide that is orthogonalto the first axis.
 6. The method of claim 5, comprising providing thetrajectories along corresponding axes that substantially intersect abouta single point in the subject adjacent to the entry portal.
 7. Themethod of claim 5, comprising providing access for viewing an entrypoint of instrument being inserted along one of the trajectories intothe subject.
 8. The method of claim 7, further comprising viewing visualindicia associated with at least one of the instrument guide and a basein determining a degree of rotation of the instrument.
 9. The method ofclaim 1, further comprising rotating the instrument guide, with respectto the entry portal, about the first axis, to obtain a desiredorientation of the instrument guide with respect to the entry portal.10. The method of claim 1, further including tailoring at least one of asize and a shape of at least one of the base and the instrument guide toorient the first axis toward the target within the subject upon securingthe base about the entry portal.
 11. The method of claim 10, in whichthe tailoring includes adjusting a height of the instrument guide withrespect to the entry portal.
 12. The method of claim 1, furtherincluding adjusting a coupling between the base and the instrument guideto adjustably orient the first axis toward the target within thesubject.
 13. A method comprising: securing an apparatus having a baseand an instrument guide relative to an entry portal of a subject, theinstrument guide defining a first lumen having a first axis and a secondlumen having a second axis, the first and second axes being fixedrelative to each other at a nonzero first angle; moving a position ofthe instrument guide with respect to the base and the entry portal suchthat a first trajectory along the first axis passes through a firstaccess point on an outer surface of the instrument guide and passessubstantially through a center of the entry portal toward a target inthe subject, the first axis defining a range plane that is orthogonal tothe first axis at a first range point on the first axis that is withinthe subject beyond the entry portal, the first axis also defining afirst distance between the first access point and the first range point;providing a second trajectory through the instrument guide along thesecond axis that passes through a second access point on the outersurface of the instrument guide and through the entry portal, to obtainthe nonzero first angle between the first and second axes, and to obtaina second distance between the second access point and a second rangepoint at an intersection between the second access and the range plane,wherein the second distance is equal to the first; and wherein moving aposition of the instrument guide with respect to the base and the entryportal includes adjusting a height between the instrument guide and theentry portal to adjust a distance between the entry portal and the rangeplane corresponding to a predetermined offset distance.
 14. The methodof claim 13, wherein moving a position of the instrument guide withrespect to the base and the entry portal includes rotating theinstrument guide with respect to the entry portal, about the first axis,to obtain a desired orientation of the instrument guide with respect tothe entry portal.
 15. A method comprising: securing an apparatus havinga base and an instrument guide relative to an entry portal of a subject,the instrument guide defining a plurality of lumens each having arespective axis, the plurality of lumens including a central lumen witha central axis, and the others of the plurality of lumens disposed aboutthe central lumen such that the plurality of lumens are disposed in acruciform arrangement, wherein each of the axes of the others of theplurality of lumens are fixed relative to the central lumen at a nonzeroangle, and wherein each of the axes of the others of the plurality oflumens intersect the central axis substantially at a common point;changing a height of the instrument guide with respect to the base andthe entry portal and rotating the instrument guide with respect to thebase and the entry portal such that a first trajectory along the centralaxis passes through a first access point on an outer surface of theinstrument guide and passes substantially through a center of the entryportal toward a target in the subject, the central axis defining a rangeplane that is orthogonal to the central axis at a first range point onthe central axis that is within the subject beyond the entry portal; andproviding a plurality of other trajectories through the instrument guidealong respective ones of the axes of the others of the plurality oflumens, the plurality of other trajectories passing through otherrespective access points on the outer surface of the instrument guideand through the entry portal.
 16. The method of claim 15, wherein atleast one of the plurality of lumens is tapered along the respectiveaxis.